Crop Specific Safety Concerns Wheat

Every crop has a different relationship to the environment, which means environmental impact assessments must be conducted on a case-by-case basis. Different crops pose different threats when it comes to out-crossing or escaping cultivation. The following plant specific characteristics are taken into account for risk assessment.

General information

Wheat (Triticum aestivum) is the most important crop in the temperate zone. The oldest traces of wheat cultivation are from the seventh pre-Christian millennium in the Middle East. With its subsequent spread to Europe, North Africa and Asia, wheat became an important crop for ancient cultures and civilisations.

“Einkorn” wheat (T. monococcum) is the oldest form of cultivated wheat; some wild forms still exist today.

The most commonly grown form of wheat in Europe is Triticum aestivum - bread wheat. Other forms of local interest are durum wheat (Triticum durum) and spelt (Triticum spelta, German wheat). Wheat forms like Triticum turgidum, “emmer” (Triticum dicoccum), or “Einkorn” (Triticum monococcum) can still be found on occasion.

Wheat is an annual plant sown in spring or in autumn. Wheat flowers from the end of May to the beginning of June. The flowers on one plant do not open simultaneously. That’s why the flowering time of a wheat cultivar can last more than a week.

Is out-crossing of transgenes from wheat possible?

Normally, self-pollination occurs, which means wheat plants fertilize themselves with their own pollen before flowers even open. Nevertheless – depending on genotype and climatic conditions – cross-pollination with other wheat plants is possible. It usually occurs at a rate of approximately one to two percent. The rate can increase up to 9.7 percent when weather conditions are dry and warm.

Wheat pollen is carried by wind. Dissemination is limited by its relatively high weight and small quantities. Furthermore, wheat pollen only remains viable for a very short period of time (a few minutes to three hours).

The genome structure of modern wheat is much different than its wild ancestors. Its set of chromosomes has multiplied - sixfold in the case of bread wheat (T. aestivum) and spelt (T. spelta). These two forms can interbreed and produce fertile offspring. The fertility of hybrids between plants with different numbers of chromosome sets is very limited. Durum wheat (T. durum, T. trugidium) and emmer wheat (T. dicoccum) have four sets of chromosomes, which makes them very unlikely to form fertile hybrids with bread wheat. The offspring of crosses with T. monococcum (two sets of chromosomes) are usually sterile.

Some cases of wheat crossing with wild relatives have been reported. Possibilities include quack grass (Agropyron), rye (Secale cereale), and several others (e.g.  Elymus, Hordeum, Leymus, Setaria, Sorghum). Most of the time, such crosses are only possible using artificial methods.

Generally speaking, the likelihood of wheat spreading transgenes to wild relatives is considered negligible.

Can wheat survive in the environment?

Wheat is adapted to a wide variety of climatic conditions. It is grown where annual temperatures of 4.9 to 27.8°C prevail. Where winters are mild, wheat can be sown in the fall and harvested the next summer. Where winters are hard, wheat must be sown in the spring because of its limited tolerance to frost. Sensitivity to frost and low competitiveness amidst wild vegetation limits its chances of survival outside of cultivated areas. Escaped wheat has not been known to become established in the wild.